LINZ, Nov 12 — Two-time Grand Slam title winner Simona Halep withdrew from her WTA Linz semi-final with a knee injury on Thursday while Danielle Collins retired after one set of her last-four clash.

As a result, Alison Riske of the United States will face Romanian lucky loser Jacqueline Cristian, ranked 100, in Friday’s final.

Second seed Halep suffered a left knee injury in her quarter-final victory on Wednesday over Jasmine Paolini.

"Unfortunately I am not able to play in my semi-final this evening after injuring my knee in my match yesterday,” Halep said in a statement.

"I would do anything to be able to play, but it is swollen and painful and playing will only make it worse.”

In the other semi-final, Collins dropped the first set to American compatriot Riske before retiring with an injured right shoulder. — AFP